I have never even NOTICED an internal pip.....I wouldn't know what to look for.
I just locked down 70 eggs yesterday. Only 4 of them had draw down air cells. Should I have waited? I lock them down more when the timing fits for me, not for them.
If you candle and see a triangle shape/shadow seemingly pressed against the shell, that's an Internal pip.
Through the membrane, breathing the air in the aircells that has hopefully grown, but not through the shell yet